Effect of soman,sarin and VX on the nicotinic acetylcholine receptor

The highly specific ligand of the N-acetylcholine receptor（N-AChR）,alpha-bungarotoxin,was used to determine the effect of soman,sarin and VX onN-AChR of the diaphragm and extensor digitorum Iongus muscle of mice andrats.The effects of the three anti-cholinesterase agents on N-AChR weredifferent.Sarin did not act directly on N-AChR and cause a change in the numberof N-AChR.VX decreased the binding sites of the receptor by binding with N-AChRdirectly.The LD50was 0.054mg/kg in mousse.Soman increased the binding sites,e.g.1～1.5 LD50soman increased the number of N-AChR of mouse diaphragm by 25%.The peak increaseof N-AChR was reached 0.5 h after poisoning and could last 96h.The receptornumber was still 22% higher than that of the control on the fourth day aftersoman poisoning in rats.Soman mainly increased the number of extrasynapticN-AChR,leading to the enhancement of sensitivity of cholinergic effectors toacetylcholine（ACh）,which is similar to the hypersensitiveness resulting fromdenervation.These findings are of significance in probing the receptor mecha-nisms and treatment of soman poisoning.